Layer system

ABSTRACT

On account of their type of coating, layer systems of the prior art often exhibit poor adhesion to the substrate. If the components are subject to high mechanical stresses, the layer can then become detached. The layer system according to the invention has separately produced anchoring means which allow stronger attachment to the substrate than the attachment of the outer layer to the substrate.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority of the European application No.04023974.1 EP filed Oct. 7, 2004, which is incorporated by referenceherein in its entirety.

FIELD OF THE INVENTION

The invention relates to a layer system.

BACKGROUND OF THE INVENTION

Nowadays, components which are intended for use at high temperatures aregenerally provided with protective layers. These may be metalliccorrosion-resistant layers (MCrAlX layers) or ceramic thermal barriercoatings, as well as layer systems comprising both metalliccorrosion-resistant layers and ceramic thermal barrier coatings.Plasma-enhanced powder spraying processes are used as the coatingprocess for these coatings, on account of their relatively favorableeconomics. Layers of this type are attached to the substrate bymechanical interlock and subsequent diffusion heat treatment. Inoperation, the layer may become detached on occasion in highly stressedregions or at unfavorable areas of the component, i.e. areas which aresubject to particularly high mechanical stresses. The layer flaking offin operation leads to damage to the base material, with the result thatthe component life is significantly reduced.

U.S. Pat. No. 5,869,798 discloses a process in which elevations areproduced on a surface by means of a welding process, the elevationconsisting of a different material than the underlying substrate.

EP 1 275 748 A2 discloses anchoring means which are arranged on asurface of a substrate or of an interlayer or project through aplurality of layers.

DE 100 57 187 A1 discloses anchoring means which project into a metallicsubstrate in order to improve the bonding of a metallic material, suchas ceramic, to the metallic substrate. The anchoring means do not extendas far as an outer surface.

EP 0 713 957 A1 discloses a process in which a recess in a layer isfilled with material.

Further prior art is known from DE 30 38 416 A1 and from Journal ofMaterials Science 24 (1989), pages 115-123, entitled “Enhancedmetal-ceramic adhesion by sequential sputter deposition and pulsed lasermelting of copper films on sapphire substrates” by A. J. Pedraza, M. J.Godbole.

SUMMARY OF THE INVENTION

Therefore, it is an object of the invention to provide a layer systemwhich has improved attachment of a protective layer to a substrateand/or of layers to one another.

The object is achieved by the layer system as claimed in the claims.

The layer system according to the invention has separately producedanchoring means, which have a very good attachment to the substrate orto an interlayer arranged below on the substrate and are attached to thesubstrate or to the other layer in a different way than the layer.

The subclaims list further advantageous measures. The measures listed inthe subclaims can be advantageously combined with one another in anydesired way.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIGS. 1, 2, 6, 7, 8 show layer systems,

FIG. 3 shows a perspective plan view of a layer system,

FIG. 4 shows process steps involved in the production of a layer system,

FIG. 5 shows process steps involved in the production of a layer system,

FIGS. 9, 20, 21, 22 show a layer system formed in accordance with theinvention,

FIGS. 10-12 show process steps involved in the production of a layersystem,

FIGS. 13, 14, 15 show process steps involved in the production of alayer system,

FIGS. 16, 17 show process steps involved in the production of a layersystem,

FIG. 18 shows a gas turbine,

FIG. 19 shows a combustion chamber, and

FIG. 23 shows a turbine blade or vane.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a layer system 1′ in accordance with the prior art. Thelayer system 1′ has a substrate 4. At least an outer layer 9 is presenton the substrate surface 5 of the substrate 4. This outer layer 9 may bea metallic and/or ceramic outer layer 9.

In accordance with the prior art, the outer layer 9 is attached to thesubstrate 4 solely by mechanical interlock (surface roughness) on theunderlying surface and a subsequent diffusion heat treatment.

Working on the basis of FIG. 1, FIG. 2 shows a layer system 1 withcontinuous anchoring means 10 or inner anchoring means 13.

The substrate 4 may be metallic or ceramic and in the case of gasturbine components is produced in particular from an iron-base,nickel-base or cobalt-based superalloy.

For turbine blades or vanes 120, 130 (FIG. 18), for example, a metalliccorrosion-resistant layer 9 (FIGS. 4, 5) of the MCrAlX type is appliedto the substrate 4, and then, for example, an outer layer, for example aceramic thermal barrier coating 9 (FIGS. 6, 7, 8), is additionallyapplied to the corrosion-resistant layer 9, so that thecorrosion-resistant layer then becomes an interlayer 7.

In the outer layer 9, there is at least one continuous anchoring means10 and/or at least one inner anchoring means 13, a certain part 14 ofwhich, for example, extends into the substrate 4.

The part 14, i.e. the extent of the continuous anchoring means 10 or ofthe inner anchoring means 13 into the substrate 4, constitutes thesmaller part, based on the length or volume of the continuous anchoringmeans 10 or of the inner anchoring means 13, so that the majority of thelength or volume of the continuous anchoring means 10 or of the inneranchoring means 13 is located in the outer layer 9.

The material of the continuous anchoring means 10 or of the inneranchoring means 13 corresponds, for example, to the material of theouter layer 9 in which it is mostly arranged. If the continuousanchoring means 10 or the inner anchoring means 13 is arranged mostly inthe outer layer 9, the material of the continuous anchoring means 10 orof the inner anchoring means 13 corresponds, for example, to thematerial of the outer layer 9. Therefore, if most of the continuousanchoring means 10 or of the inner anchoring means 13 is located in theinterlayer 7 (FIGS. 6, 7, 8), the material of the continuous anchoringmeans 10 or of the inner anchoring means 13 corresponds, for example, tothe material of the interlayer 7. The continuous anchoring means 10 orthe inner anchoring means 13 in particular have a different type ofattachment, in particular with an increased attachment force (morespecifically: force per unit contact area) to the substrate 4 or to theinterlayer 7 than the type of attachment of the interlayer 7 to thesubstrate 4 or of the outer layer 9 to the interlayer 7.

The continuous anchoring means 10 or the inner anchoring means 13, byway of example, are attached to the substrate 4 by melt metallurgy usinga suitably managed laser welding process. It is also conceivable for theouter layer 9 to be applied to defined locations by laser cladding(laser powder coating) and in this way to form continuous anchoringmeans 10 or inner anchoring means 13. The continuous anchoring means 10or inner anchoring means 13 can also be cast on or produced integrallyduring casting of the substrate 4.

The continuous anchoring means 10 or inner anchoring means 13 constitutebonding bridges for the outer layer 9 surrounding the continuousanchoring means 10 or inner anchoring means 13. The continuous anchoringmeans 10 start from the substrate surface 5 of the substrate 4 andextend only as far as the outer surface 16 of the outer layer 9 (or ifappropriate out of the substrate 4 if a part 14 is present).

The inner anchoring means 13 are covered by the outer layer 9, andconsequently the inner anchoring means 13 do not extend as far as theouter surface 16 of the outer layer 9, i.e. are arranged so as to endwithin the outer layer 9. In this case, they 13 extend into the outerlayer 9 over at least 10%, 20%, 30%, 40% or more of the thickness of theouter layer 9.

A corresponding statement also applies to the continuous anchoring means10 or inner anchoring means 13 in the interlayer 7.

It is also possible for only continuous anchoring means 10 or only inneranchoring means 13 to be present in the outer layers 9.

The continuous anchoring means 10 or the inner anchoring means 13 are,for example, only present in locally limited form (FIG. 3) on thesubstrate 4 or the interlayer 7, namely where the mechanical stressesare highest. This is, for example, the region of the leading edge 409(FIG. 24) of a turbine blade or vane 120, 130. The remaining blade orvane part 406 (FIG. 24) would not then have any continuous anchoringmeans 10 or inner anchoring means 13.

FIG. 3 shows a plan view of an inner surface 8 of the interlayer 7 or ofan outer surface 16 of the outer layer 9. The inner anchoring means 13,which do not extend as far as the inner surface 8 (FIG. 6) of theinterlayer 7, are indicated by dashed lines.

The continuous anchoring means 10 or the inner anchoring means 13 mayhave different geometries, such as circles, quilted-seam profiles (i.e.they are elongate and cross one another), wave shapes, parallel tracksand combinations thereof on the substrate surface 5.

FIG. 6 shows a further layer system 1. The layer system 1 comprises asubstrate 4, an interlayer 7 and an outer layer 9. The interlayer 7 is,for example, a metallic MCrAlX layer, and the outer layer 9 is, forexample, a ceramic thermal barrier coating 9 on the interlayer 7.

Continuous anchoring means 10 or inner anchoring means 13 are presentboth in the interlayer 7 and in the outer layer 9.

The interlayer 7, however, does not have to have continuous anchoringmeans 10 or inner anchoring means 13 (FIG. 8). It is likewise possiblefor the anchoring means to be present only in the interlayer 7 (FIG. 7).

In this case, some or even all of the continuous anchoring means 10 orinner anchoring means 13 in the interlayer 7 and/or the outer layer 9may have a part 14 which extends into the substrate 4 or the interlayer7.

The continuous anchoring means 10 in the interlayer 7 or in the outerlayer 9, starting from the substrate surface 5 of the substrate 4 orfrom the inner surface 8 of the interlayer 7, extend as far as the innersurface 8 of the interlayers 7 or as far as the outer surface 16 of theouter layer 9, but not beyond, or they 13 are covered by the interlayer7 or the outer layer 9, so that the inner anchoring means 13 do notextend as far as the inner surface 8 of the interlayer 7 or the outersurface 16 of the outer layer 9.

The continuous anchoring means 10 or inner anchoring means 13 in theinterlayer 7 improve the attachment of the interlayer 7 to the substrate4. The material of the continuous anchoring means 10 of the interlayer 7may, for example, also be selected in such a way as to produce improvedbonding of the outer layer 9 to the anchoring means 10 (FIG. 7).

The material composition of the continuous anchoring means 10 or inneranchoring means 13 in the interlayer 7 or the outer layer 9 is selectedappropriately according to the particular demands.

The material of the continuous anchoring means 10 or inner anchoringmeans 13, for example, corresponds to the material of the interlayer 7or of the outer layer 9 in which it is mostly arranged.

Therefore, if the continuous anchoring means 10 or inner anchoring means13 is located largely in the interlayer 7, the material of thecontinuous anchoring means 10 or of the inner anchoring means 13corresponds, for example, to the material of the interlayer 7. If thecontinuous anchoring means 10 or the inner anchoring means 13 isarranged largely in the outer layer 9, the material of the continuousanchoring means 10 or of the inner anchoring means 13 corresponds, forexample, to the material of the outer layer 9.

The continuous anchoring means 10 or inner anchoring means 13 arepresent in particular in regions which are subject to high thermaland/or mechanical stresses.

In the case of turbine blades or vanes, this means the leading edge 409,the trailing edge 412 (FIG. 24) or the transition between the main bladeor vane part 406 and the platform 403 (FIG. 24).

The layer system 1 is, for example, a component of a gas turbine 100(FIG. 18) (or aircraft turbine) or of a steam turbine. Components of theturbines which are subject to high thermal stresses have a layer systemof this type, for example turbine blades or vanes 120, 130, heat shieldelements 155 of a combustion chamber 110 and further casing parts whichare located along the flow path of a hot steam or hot gas.

The layer system 1 can be applied to a newly produced component and tocomponents which are refurbished after use. In the latter case, thecomponents first of all have degraded layers removed from them, anycracks repaired, and then the substrate 4 is recoated.

FIG. 7 shows a further exemplary embodiment of a layer system 1. In thislayer system 1, the continuous anchoring means 10 or inner anchoringmeans 13 are present only in the interlayer 7. The outer layer 9 ispresent on the interlayer 7. A contact surface of the continuousanchoring means 10 against the inner surface 8 improves the bonding ofthe outer layer 9 compared to a comparable contact surface with theinterlayer 7. This is achieved, for example, by virtue of the fact thatthe contact surfaces of the continuous anchoring means 10 form nuclei,for example of aluminum oxide, at the inner surface 8 for epitaxialgrowth, for example, of an outer layer 9 on the interlayer 7. Evenwithout interlayer 7 (FIGS. 4, 5, right-hand side), an improved layersystem 1 is achieved by virtue of the fact that the continuous anchoringmeans 10 or the inner anchoring means 13 lead to improved attachment ofthe outer layer 9 to the substrate 4.

In this context, it is not necessary for some or not imperative for allof the continuous anchoring means 10 or inner anchoring means 13 to havea part 14 extending into the substrate 4.

FIG. 8 shows a further exemplary embodiment of a layer system 1. Thecontinuous anchoring means 10 or inner anchoring means 13 are onlypresent in the outer layer 9 in this exemplary embodiment.

In this case, some but not necessarily all of the continuous anchoringmeans 10 or inner anchoring means 13 extend into the substrate 4 or intothe interlayer 7.

By way of example, FIG. 4 shows process steps involved in a process forproducing a layer system 1. In a first step, the at least one outerlayer 9 is applied to the substrate 4 in a known way.

The outer layer 9 is treated, for example, with a laser 17 or anelectron beam gun 17, which emits a corresponding laser or electron beam19. As a result of this type of treatment, the material of the outerlayer 9 is locally converted, for example partially melted, down to thesubstrate surface 5 of the substrate 4 or even beyond it by way of apart 14 into the substrate 4, so as to produce melt-metallurgicalattachment of material from the outer layer 9 into the substrate 4. Thisprocess produces continuous anchoring means 10 which extend from thesubstrate surface 5 to the outer surface 16 of the outer layer 9.

The statements which have been made in connection with the outer layer 9(without interlayer 7) apply similarly to an interlayer 7 to which anouter layer 9 is also applied.

FIG. 5 shows a further production process. In a first step, first of allthe continuous anchoring means 10 or inner anchoring means 13 areapplied to the substrate 4, i.e. produced separately. This can be donein various ways, such as for example by means of a suitably guided laserwelding process or laser cladding. The continuous anchoring means 10 orinner anchoring means 13 in particular have a very strong attachment, inparticular by melt metallurgy, to the substrate 4.

However, the continuous anchoring means 10 or inner anchoring means 13may also already have been produced during production of the substrate4, for example by a casting process.

In a subsequent process, the outer layer 9 is applied, with thecontinuous anchoring means 10 or inner anchoring means 13 beingsurrounded by the material of the outer layer 9 and forming bondingbridges for the layer 9.

The material of the continuous anchoring means 10 or inner anchoringmeans 13 may be the same as the material of the outer layer 9 or thesame as the material of the substrate 4 or may alternatively also have adifferent material composition.

The statements which have been made in connection with the outer layer 9(without interlayer 7) apply in a similar way to an interlayer 7 towhich an outer layer 9 is also applied.

FIG. 9 a shows a component 1 according to the invention (cross sectionthrough a continuous anchoring means 10). The continuous anchoring means10 has a larger cross-sectional area 11 at the outer surface 16 than atthe substrate surface 5 below (FIG. 9 b, plan view of FIG. 9 a).

The shape of the continuous anchoring means 10 in cross section is inthis case, for example, in the form of a bell. The cross-sectionalcontour may also take other shapes, such as for example a parabolicprofile, in which case the parabola is open at the top 16 (FIG. 9 b).

The cross section of the continuous anchoring means 10 is in this case,by way of example, round in form (FIG. 9 b). Other cross sections arepossible (oval). The cross-sectional area of the continuous anchoringmeans 10 at the substrate surface 5 is indicated by dashed lines.

In this case, the continuous anchoring means 10 may likewise extend intothe substrate 4 (not shown).

The material of the continuous anchoring means 10 may, in the outerlayer 9, for example, correspond to the material of the substrate 4(metallic) or may be ceramic.

In particular, the material of the outer layer 9 consists of an alloy ofthe MCrAlX type, in which case the anchoring means 10 include a materialof an alloy of the MCrAlX type, which corresponds to that of the outerlayer 9 or has been modified.

FIG. 20 shows a further exemplary embodiment of a component 1 accordingto the invention. The layer system 1 comprises a substrate 4, aninterlayer 7 and an outer layer 9. The substrate 4 is, for example, asuperalloy, and the interlayer 7 consists of an alloy of the MCrAlXtype, to which an outer ceramic thermal barrier coating 9 has then beenapplied. Likewise, as illustrated in FIG. 9 a, in this case thecontinuous anchoring means 10 are formed only in the interlayer 7.

In FIG. 21, the continuous anchoring means 10 is arranged only in theouter layer 9. In FIG. 22, the continuous anchoring means 10 arearranged both in the interlayer 7 and in the outer layer 9.

Furthermore, inner anchoring means 13 may also be present in theexemplary embodiments shown in FIGS. 9, 20 to 22.

Should the outermost layer 9 flake off or have local damage in theregion of the continuous anchoring means 10, the continuous anchoringmeans 10 ensures that the interlayer 7 remains on the substrate 4 andthe substrate 4 is still protected.

The material of the continuous anchoring means 10 may also be selectedin such a way that it serves as a growth nucleus, in particular forepitaxial growth, when coating the interlayer 7 with the material of theouter layer 9, for example a ceramic material. In particular, thematerial of the interlayer 7 consists of an alloy of the MCrAlX type, inwhich case the anchoring means 10 likewise consist of an alloy of theMCrAlX type, which may if appropriate have been modified with respect tothe composition of the interlayer 7.

In particular, the material class of the continuous anchoring means 10or of the inner anchoring means 13 corresponds to the material class ofthe interlayer 7 or of the outer layer 9 in which it is arranged: metalor ceramic.

FIGS. 10 to 12 show a process for producing the layer system 1.

The outer layer 9 and the continuous anchoring means 10 or inneranchoring means 13 are produced, for example, in layers, i.e. the outerlayer 9 is produced, and thereafter or simultaneously the continuousanchoring means 10 or the inner anchoring means 13 are produced. On noaccount are the anchoring means at least mostly or completely producedfirst of all (FIG. 5), followed by the layer, or vice-versa (FIG. 4).

Therefore, starting from the substrate 4, which does not yet have anyouter layer 9, material for the outer layer 9 is applied in layers, andthe continuous anchoring means 10 or inner anchoring means 13 arelikewise produced in layers. Depending on whether continuous anchoringmeans 10 or inner anchoring means 13 are produced, laser heating, forexample, is applied at the locations where a continuous anchoring means10 or inner anchoring means 13 is to be formed, melting the material,i.e. temporarily and locally increasing the temperature.

If an inner anchoring means 13 is to be produced (FIG. 11), which is notintended to extend as far as the outer surface 16 of the layer 9, beyonda certain height the outer layer 9 is no longer melted locally (FIG.12).

The statements made in connection with the outer layer 9 (withoutinterlayer 7) apply in a corresponding way for an interlayer 7, to whichan outer layer 9 is also applied.

FIGS. 13 to 15 show a further production process.

In this case, an outer layer 9 is already present on the substrate 4.This is the case in particular if the component 1 is a component whichis to be repaired, i.e. has already been used and in particular haslocal damage in the form of a recess 34.

This recess 34 has, for example, been weakened or was exposed to highdemands in use, and in a first step is treated for example by means of alaser 17 (or electron beam gun) and its laser beams 19 (FIG. 13), sothat continuous anchoring means 10 or inner anchoring means 13 areformed (FIG. 14).

In a further process step, the recess 34 is filled with layer material25 from a material feed 22 (for example powder feed), for example bylaser build-up welding, in which case either only layer material 25forms the filling, without the inner anchoring means 13 shown in FIG. 14being formed any further, so as to produce an inner anchoring means 13which does not extend as far as the outer surface 16, or alternatively,for example, the laser 17 for the laser build-up welding is also used,for example, to allow the continuous anchoring means 10 shown in FIG. 14to grow as far as the outer surface 16.

The continuous anchoring means 10 or inner anchoring means 13 may butdoes not have to have a part 14 (indicated by dashed lines) extendinginto the substrate 4, or may be of the form shown in FIG. 9.

The layer material 25 may be material of the outer layer 9 or of thesubstrate 4, but may also have a different composition. Also, it ispossible for an outer layer 9 to be locally absent in the recess 34 andfor material of, for example, the outer layer 9 to be applied, producingcontinuous anchoring means 10 or inner anchoring means 13.

The statements made in connection with the outer layer 9 (withoutinterlayer 7) apply in a corresponding way to an interlayer 7 to whichan outer layer 9 is also applied.

FIGS. 16, 17 show a further exemplary embodiment of a process forproducing a layer system 1.

By way of example, a plasma torch 31 (FIG. 16) is used to produce theouter layer 9.

By means of a laser 17 and its laser beams 19, a continuous anchoringmeans 10 or inner anchoring means 13 is produced, for examplesimultaneously, for example by melting, as a result of the materialbeing treated by means of the laser 17, i.e. for example partiallymelted, at least from time to time at the locations intended for thecontinuous anchoring means 10 or inner anchoring means 13.

It is also possible to use two lasers 17, 17′ (FIG. 17), in which caseone laser 17′ is used for the build-up process, for example laserbuild-up welding with the aid of a material feed 22, which delivers thelayer material 25, and a laser 17 which, as in FIG. 16, produces thecontinuous anchoring means 10 or inner anchoring means 13.

The statements made in connection with the outer layer 9 (withoutinterlayer 7) correspondingly also apply to an interlayer 7 to which anouter layer 9 is subsequently applied.

In FIGS. 13, 14, 15, 16 and 17, the interlayer 7 or the outer layer 9and the continuous anchoring means 10 or inner anchoring means 13 can beproduced in layers.

It is also possible for electron beam guns to be used instead of thelasers 17, 17′ or plasma torches 31. The use of lasers, plasma torchesis not restricted to the embodiments on continuous anchoring means 10 orinner anchoring means 13 which have a part 14 extending into thesubstrate 4 or into the interlayer 7 or to a specific cross-sectionalshape as shown in FIG. 9.

FIG. 18 shows a gas turbine 100 in longitudinal part section. In theinterior, the gas turbine 100 has a rotor 103 which is mounted so as torotate about an axis of rotation 102 and is also referred to as theturbine rotor. An intake casing 104, a compressor 105, a, for example,torroidal combustion chamber 110, in particular an annular combustionchamber 106, with a plurality of coaxially arranged burners 107, aturbine 108 and the exhaust-gas casing 109 follow one another along therotor 103. The annular combustion chamber 106 is in communication witha, for example, annular hot-gas duct 111. There, by way of example, fourturbine stages 112 connected in series form the turbine 108. Eachturbine stage 112 is formed from two blade or vane rings. As seen in thedirection of flow of a working medium 113, a row 125 of rotor blades 120follows a row 115 of guide vanes in the hot-gas duct 111.

The guide vanes 130 are in this case secured to the stator 143, whereasthe rotor blades 120 of a row 125 are arranged on the rotor 103 by meansof a turbine disk 133. A generator (not shown) is coupled to the rotor103.

While the gas turbine 100 is operating, the compressor 105 sucks in air135 through the intake casing 104 and compresses it. The compressed airwhich is provided at the turbine-side end of the compressor 105 ispassed to the burners 107, where it is mixed with a fuel. The mixture isthen burnt, forming the working medium 113 in the combustion chamber110. From there, the working medium 113 flows along the hot-gas duct 111past the guide vanes 130 and the rotor blades 120. The working medium113 expands at the rotor blades 120 in such a manner as to transfer itsmomentum, so that the rotor blades 120 drive the rotor 103 and thelatter drives the generator coupled to it.

When the gas turbine 100 is operating, the components exposed to the hotworking medium 113 are subject to thermal stresses. The guide vanes 130and rotor blades 120 of the first turbine stage 112, as seen in thedirection of flow of the working medium 113, together with the heatshield bricks which line the annular combustion chamber 106, are subjectto the highest thermal stresses. To be able to withstand thetemperatures prevailing there, these components are cooled by means of acooling medium. It is likewise possible for the blades or vanes 120, 130to have coatings protecting against corrosion (MCrAlX; M=Fe, Co, Ni,X=Y, rare earths) and heat (thermal barrier coating, for example ZrO₂,Y₂O₄—ZrO₂).

The guide vane 130 has a guide vane root (not shown here) facing theinner casing 138 of the turbine 108 and a guide vane head at theopposite end from the guide vane root. The guide vane head faces therotor 103 and is fixed to a securing ring 140 of the stator 143.

FIG. 19 shows a combustion chamber 110 of a gas turbine 100. Thecombustion chamber 110 is configured, for example, as what is known asan annular combustion chamber, in which a multiplicity of burners 107,which are arranged around the turbine shaft 103 in the circumferentialdirection, open out into a common combustion chamber space. For thispurpose, the combustion chamber 110 as a whole is configured as anannular structure which is positioned around the turbine shaft 103.

To achieve a relatively high efficiency, the combustion chamber 110 isdesigned for a relatively high temperature of the working medium M ofapproximately 1000° C. to 1600° C. To allow a relatively long operatingtime even under these operating parameters, which are unfavorable forthe materials, the combustion chamber wall 153 is provided, on its sidewhich faces the working medium M, with an inner lining formed from heatshield elements 155. On the working medium size, each heat shieldelement 155 is equipped with a particularly heat-resistant protectivelayer or is made from material that is able to withstand hightemperatures. Moreover, on account of the high temperatures in theinterior of the combustion chamber 110, a cooling system is provided forthe heat shield elements 155 and/or for their holding elements.

FIG. 24 shows a perspective view of a rotor blade 120 or guide vane 130of a turbomachine, which extends along a longitudinal axis 121.

The turbomachine may be a gas turbine of an aircraft or a power plantfor power generation, a steam turbine or a compressor.

The blade or vane 120, 130 includes, in succession along thelongitudinal axis 121, a securing region 400, an adjoining blade or vaneplatform 403 and a main blade or vane part 406. When used as guide vane130, the vane 130 may have a further platform at its vane tip 415 (notshown).

A blade or vane root 183, which is used to secure the rotor blades 120,130 to a shaft or a disk (not shown), is formed in the securing region400. The blade or vane root 183 is configured, for example, inhammerhead form. Other configurations, as a fir tree root or dovetailroot are possible. The blade or vane 120, 130 has a leading edge 409 anda trailing edge 412 with a respect to a medium which flows past the mainblade or vane part 406.

In the case of conventional blades or vanes 120, 130, by way of examplesolid metallic materials, in particular superalloys, are used in allregions 400, 403, 406 of the blade or vane 120, 130. Superalloys of thistype are known, for example, from EP 1 204 776 B1, EP 1 306 454, EP 1319 729 A1, WO 99/67435 or WO 00/44949; these documents form part of thepresent disclosure with regard to the chemical composition of the alloy.The blade or vane 120, 130 may in this case be produced by a castingprocess, also by means of directional solidification, by a forgingprocess, by a milling process or by combinations thereof.

Workpieces with a single-crystal structure or structures are used ascomponents for machines which are exposed to high mechanical, thermaland/or chemical stresses in operation. Single-crystal workpieces of thistype are produced, for example, by directional solidification from themelt. This involves casting processes in which the liquid metallic alloysolidifies to form the single-crystal structure, i.e. the single-crystalworkpiece, or directionally. Dendritic crystals are formed along thedirection of heat flow and form either a columnar grain structure (i.e.grains which run over the entire length of the workpiece and arereferred to here, in accordance with the usual terminology, asdirectionally solidified) or a single-crystal structure, i.e. the entireworkpiece comprises a single crystal. In these processes, transition tothe globular (polycrystalline) solidification needs to be avoided, sincenon-directional growth inevitably leads to the formation of transverseand longitudinal grain boundaries which negate the good properties ofthe directionally solidified or single-crystal component. Wherever thetext refers in general terms to directionally solidifiedmicrostructures, this is also to be understood as encompassing singlecrystals which do not have any grain boundaries or at most havesmall-angle grain boundaries, as well as columnar crystal structures,which do have grain boundaries running in the longitudinal direction butdo not have any transverse grain boundaries. This second type ofcrystalline structures is also referred to as directionally solidifiedmicrostructures (directional solidified structures). Processes of thistype are known from U.S. Pat. No. 6,024,794 and EP 0 892 090 A1; thesedocuments form part of the disclosure.

It is also possible for the blades or vanes 120, 130 to have coatingsprotecting against corrosion or oxidation (MCrAlX; M is at least oneelement selected from the group consisting of iron (Fe), cobalt (Co),nickel (Ni), X is an active element and stands for yttrium (Y) and/orsilicon and/or at least one of the rare earth elements, or hafnium(Hf)). Alloys of this type are known from EP0486489 B1, EP0786017 B1, EP0 412 397 B1 or EP 1 306 454 A1, which are intended to form part of thepresent disclosure with regard to the chemical composition of the alloy.

It is also possible for a thermal barrier coating consisting, forexample, of ZrO₂, Y₂O₄—ZrO₂—i.e. this coating is not stabilized, ispartially stabilized or is completely stabilized by yttrium oxide and/orcalcium oxide and/or magnesium oxide—to be present on the MCrAlX.Columnar grains are produced in the thermal barrier coating by suitablecoating processes, such as for example electron beam physical vapordeposition (EB-PVD).

Refurbishment means that components 120, 130, after they have been used,if appropriate have protective layers removed (e.g. by sand blasting).Then, the corrosion and/or oxidation layers and products are removed.Any cracks in the component 120, 130 are also repaired. Then, thecomponent 120, 130 is recoated and the component 120, 130 is reused.

The blade or vane 120, 130 may be hollow or solid in form. If the bladeor vane 120, 130 is to be cooled, it is hollow and may also have filmcooling holes 418 (indicated by dashed lines).

1-29. (canceled)
 30. A layer system, comprising: a substrate having asubstrate surface; an outer layer arranged on the substrate and havingan outer surface spaced apart from the substrate surface of thesubstrate; a continuous anchoring device arranged in the outer layerthat does not extend in the outer layer beyond the outer surface and across-sectional area of the continuous anchoring device is larger at theouter surface than at the substrate surface; and an inner anchoringdevice arranged in the outer layer that extends within at least 10% ofthe thickness of the outer layer.
 31. The layer system as claimed inclaim 30, wherein the continuous anchoring device or the inner anchoringdevice are joined to the substrate by melt metallurgy.
 32. The layersystem as claimed in claim 30, wherein the material of the continuousanchoring device or the inner anchoring device in the outer layercorresponds to the material of the outer layer
 33. The layer system asclaimed in claim 30, wherein the material of the continuous anchoringdevice or the inner anchoring device is different than the material ofthe outer layer.
 34. The layer system as claimed in claim 30, whereinthe continuous anchoring device or the inner anchoring device arepresent only locally on the substrate.
 35. The layer system as claimedin claim 30, wherein the continuous anchoring device or the inneranchoring device are columnar in form.
 36. The layer system as claimedin claim 30, further comprising an interlayer arranged between thesubstrate surface and the outer layer, having an inner surface oppositethe substrate surface.
 37. The layer system as claimed in claim 36,wherein the continuous anchoring device or the inner anchoring deviceare present in the outer layer or the interlayer.
 38. The layer systemas claimed in claim 36, wherein the continuous anchoring device or theinner anchoring device have a different form of attachment to thesubstrate or to the interlayer than the outer layer to the interlayer orthe interlayer to the substrate.
 39. The layer system as claimed inclaim 36, wherein the continuous anchoring device extend as far as theinner surface of the interlayer or as far as the outer surface of theouter layer.
 40. The layer system as claimed in claim 36, wherein thecontinuous anchoring device does not extend beyond the inner surface ofthe interlayer, or The outer surface of the outer layer.
 41. The layersystem as claimed in claim 36, wherein the interlayer is an MCrAlXlayer.
 42. The layer system as claimed in claim 30, wherein the layersystem is a new or refurbished turbine component.
 43. A layer system,comprising: a substrate having a substrate surface; an outer layerarranged on the substrate and having an outer surface spaced apart fromthe substrate surface of the substrate; and a continuous anchoringdevice in the outer layer, wherein the continuous anchoring deviceextends in the outer layer as far as the outer surface andcross-sectional area of the continuous anchoring device is larger at theouter surface than at the substrate surface.
 44. The layer system asclaimed in claim 43, further comprising an interlayer arranged betweenthe substrate surface and the outer layer and having an inner surfaceopposite the substrate surface.
 45. The layer system as claimed in claim44, wherein the interlayer is an MCrAlX layer.
 46. The layer system asclaimed in claim 44, wherein an inner anchoring device extends onlywithin at least 10% of the thickness of the interlayer or only within atleast 10% of the thickness of the outer layer.
 47. The layer system asclaimed in claim 46, wherein the continuous anchoring device or theinner anchoring device are columnar in form.
 48. The layer system asclaimed in claim 44, wherein the continuous anchoring device does notextend beyond the inner surface of the interlayer, or The outer surfaceof the outer layer.
 49. The layer system as claimed in claim 43, whereinthe layer system is a new or refurbished turbine component.